The present invention relates to a method for producing glass fibers (fibrous glass wool) with centrifugal force and an apparatus therefor.
The method for producing glass fibers with centrifugal force is generally to supply a molten glass flow or stream to a rotating body, which is supported on a vertical shaft, and to radially spout the molten glass from the periphery thereof by the centrifugal force so as to divide and elongate or attenuate the glass into fibers.
The glass flow elongated in this way is flowed downwards in the vicinity of the outer circumference of the rotary body, usually coated with a binder, and then collected on the surface of a porous collecting conveyer provided below the rotary body. A suction chamber is provided usually below the collecting conveyer for forming the glass into a mat, blanket or other form. The cotton-like product thus formed is finally subjected to such treatments as forming, hardening, processing and packing with the use of an aftertreatment apparatus to produce a final product.
Now, as a rotary body, a cylindrical cage-type hollow body having a plurality of orifices with a diameter of 0.2 to 1.2 mm in a multi-stage manner around the total peripheral wall thereof has usually been adopted. In order to avoid violent erosion and deformation of the hollow body, the quality of the glass composition to be applied should have an appropriate viscosity-temperature characteristic so that the melt passes through the orifices easily at a prescribed low temperature range. For example, in the case of a low-alkaline glass fiber material, a large quantity of such compounds as compounds of barium, boron and fluorine has usually been added as a flux for the purpose of lowering the melting and spinning temperatures. However, the compounds of boron and fluorine are usually volatile at the temperature of melting and spinning, so that an excess of them must be added in consideration of the volatilization loss. Thus, the production cost becomes high, and particularly, since fluorine compounds cause public pollution, a particular exhaust gas treating apparatus is needed. Barium compounds are not only costly but also erode the furnace refractories violently.
Furthermore, in a conventional cylindrical cage-type rotary body, the inner surface of the outer peripheral wall and the orifices are always at a temperature above 1200.degree. C. in contact with molten glass. At this temperature a usual heat resistant steel has inferior durability, and therefore a Ni-Cr-Co type super heat resisting steel or a noble metal such as platinum must be employed. These metals are not only difficult to work, but are also costly.